1. Field
One or more embodiments of the present invention relate to a method of manufacturing a retainer ring for polishing a wafer, and more particularly, to a method of manufacturing a retainer ring for retaining an outer circumferential surface of a wafer during a process of polishing a wafer by using a chemical mechanical polishing (CMP) method.
2. Description of the Related Art
The manufacture of a semiconductor device essentially includes a polishing process for planarizing a surface of a semiconductor wafer.
As the polishing process, a chemical mechanical polishing (CMP) method is mainly used. According to the CMP method, a surface of a wafer coated with tungsten or oxide or the like is polished by mechanical friction and also by using a chemical abrasive. In the CMP method, a wafer fixed to a carrier is pressed against a polishing pad and rotated so that a surface of the water is polished by friction between the polishing pad and the surface of the wafer. In addition, the surface of the wafer is chemically polished by a slurry which is supplied between the polishing pad and the wafer as a chemical abrasive.
FIG. 1 is a schematic view to explain a process of polishing a wafer by using a CMP method. A polishing pad 2 is installed on a turntable 1, and a wafer W is placed on the polishing pad 2. The wafer W is contacted to a lower surface of a carrier 3 that accommodates the wafer W, and then, the wafer W is supported by using a retainer ring 9 so that the wafer W is not separated from the carrier 3 which operates by using a driving unit 4, during polishing. By supplying a slurry 6, which is an abrasive, between the wafer W and the polishing pad 2 through a nozzle 5, while pressurizing the wafer W accommodated in the carrier 3 against the polishing pad 2 with a predetermined pressure, the wafer W is polished both chemically and mechanically by rotation of the polishing pad 2.
The retainer ring 9 for polishing a wafer, according to the conventional art, includes a frame ring 7 and a polishing ring 8. The frame ring 7 is formed of a metal, and the polishing ring 8 is formed of a synthetic resin material. The frame ring 7 and the polishing ring 8 are coupled to each other by using an adhesive. Referring to FIG. 1, the polishing ring 8 is rotated while being pressurized against the polishing pad 2, and is worn away together with the wafer W due to friction. That is, the polishing ring 8 is a consumable component which is worn away and is reduced in height when used for a long period of time. When the lifespan of the polishing ring 8 ends, the polishing ring 8 is cut away from the frame ring 7 by using a cutting tool, and another new polishing ring 8 is contacted to the frame ring 7 for use.
However, since the frame ring 7 and the polishing ring 8 are coupled to each other by using an adhesive, when cutting the polishing ring 8 from the frame ring 7 by using a cutting tool, not just the polishing ring 7 which is formed of a synthetic resin is cut but a portion of the frame ring 8 is also cut. Thus, when a polishing ring is replaced regarding a frame ring several times, dimensions and a shape of the frame ring are changed and the frame ring becomes unusable in the end. This shortens a replacement period of the frame ring, and the costs of the CMO method are also increased.
In addition, the frame ring 7 and the polishing ring 8 may be separated from each other as an adhesive force of the adhesive in the CMP process is weakened, and this may damage a wafer and cause a great loss in the CMP method.
In addition, a polishing ring is manufactured using a resin such as polyether ether ketone (PEEK), polyethylene (POM), polyphenylene sulfide (PPS), polyamide imide (PAI), or polyether imide (PEI), which are high-functional resins having resistance to polishing and are thus highly expensive. As a retainer ring is replaced although just a small portion of the polishing ring is worn, an expensive polishing ring resin is consumed unnecessarily, increasing the total manufacturing costs.